1. Technical Field
A recirculation system is disclosed for paint colorants used in automated paint dispensing and paint formulation machines. The recirculation system prevents the settling out of heavier materials such as pigments of a colorant (i.e., tint) slurry or formulation. The recirculation system provides recirculation up to the nozzle outlet.
2. Description of the Related Art
Systems for dispensing a plurality of different fluids into a container are known. For example, systems for dispensing paint base materials and colorants into a paint container are known. These paint systems may use twenty or more different colorants to formulate a paint mixture. Each colorant is contained in a separate canister or package and may include its own dispense pump. The colorants and their respective pumps may be disposed on a turntable or along one or more stationary horizontal rows. In a turntable system, the turntable is rotated so that the colorant to be dispensed is moved to a position above the container being filled. In designs using one or more horizontal rows, the container may be moved laterally to the appropriate colorant/pump or the colorants may be dispensed through a manifold.
In paint dispensing applications, precision is essential as the color formulations or paint formulations require the addition of precise amounts of tints or colorants. One way in which the precision of a paint dispensing systems is compromised when the condition of a colorant or tint becomes non-uniform as a result of a settling out of heavier components of the colorant slurry during storage in the canister prior to dispensing or between dispenses.
Specifically, the actual pigments of a colorant slurry tend to be heavier than the remaining components, such as the solvent. As these heavier materials gather or collect towards the bottom of the canister under the force of gravity, the colorant slurry has non-uniform concentrations of the various ingredients from the bottom of the canister to the top of the canister. As a result, the heavier pigment materials may be dispensed in a higher concentration when the canister is relatively full and at a lower concentration when the canister is close to being empty. The non-uniformity of the colorant slurry leads to inaccuracies in the final paint formulation.
This problem is exacerbated by the reduced amounts of volatile organic compounds (VOCs) being used in some colorants and the VOC-free colorants. In short, the low-VOC and VOC-free colorant slurries have a higher tendency to separate or settle out than the VOC-based colorants, such as glycol-based colorants. While separation takes place in glycol-based colorants, the separation typically takes longer to occur.
Currently available paint dispensing machines employ agitation devices within the colorant canisters to prevent settling. The agitation devices are activated periodically by software programmed into the controller of the machine. However, colorant disposed in the sections of tubing between the canister and the pump and between the pump and the outlet, i.e., the dispense valve, manifold or nozzle, are not agitated. As a result, the colorant in the tubing, manifold, dispense valve or other areas of the system outside of the canister will separate over time and affect the accuracy of the dispense.
Further, if the dispense pumps are not used relatively frequently, low VOC, VOC-free and even glycol-based colorants may settle inside of the pump. The accumulation of the solid particles can cause many types of pumps to jam or at least operate inefficiently.
As a result, there is a need for an improved colorant canister and dispense system for use in automated paint dispensing machines that avoids the settling problem, regardless of the colorant, solvent and pump type. Further, there is a need for an improved colorant canister and dispense system for use in automated paint dispensing machines that provides recirculation in the tubing between the canister and the dispense outlet, including any dispense valves and the dispense pump. All of these components are prone to having low-VOC colorant settle within them causing clogging, uneven flow rates and requiring frequent maintenance.